Will Google’s mobile algorithm changes hurt Fortune 500 websites’ search results ranking? Many have their work cut out for them, based on Q1 2015 research by Merkle | RKG.

The study found that nearly half of Fortune 500 websites were not mobile-friendly according to Google’s standards. Internet Retailer Top 500 websites were in a far better position, likely due to demand from digital consumers for mobile-optimized sites over the past few years. Even Fortune 500 companies that did have Google-approved mobile sites weren’t necessarily following Google’s recommendation to use responsive design; 70% were using m. or distinct mobile URLs.

Google’s new algorithm will likely force Fortune 500 sites to finally get on the mobile optimization train; otherwise, their lack of mobile-friendly requirements will negatively affect their rank in results, RKG noted. Q4 2014 research by AdLift highlighted the importance of ranking highly, as clickthrough rates (CTRs) for US mobile organic search results dropped drastically for those not in the first position. For example, results for branded keywords fell from 46.4% CTR for position one to 10.8% for position two.

Google’s stronger stress on mobile optimization coincides with mobile’s increasing share of traffic on the search engine. RKG found that in Q1 2015, 47% of Google’s North America organic traffic was driven by mobile—up 3 percentage points quarter over quarter and 11 points year over year. Across all engines, search traffic driven by mobile rose 54% in the first quarter of this year, vs. 14% for overall search visits.

For the first time next year, eMarketer estimates, the majority of US consumers will conduct a search on a mobile phone at least once per month, with that figure coming in at 49.0% this year. By 2019, 65.0% of the US population will be mobile phone search users, representing nearly eight in 10 mobile phone users.